Answer:
4. ± 3.012
Step-by-step explanation:
Hello!
Assuming that for both variables X₁ and X₂ n₁= n₂ = 16
You need to test at 1% if the variable is significant, this means, if the slope for X₁ is different from zero (β₁≠0) using the t-statistic and the critical value approach.
The hypotheses are:
H₀: β₁= 0
H₁: β₁≠ 0
α: 0.01

The degrees of freedom "n₁-3" are determined by the number of parameters that you estimate for the multiple regression, in this case there are three "β₁" "β₂" and "δ²e"
The rejection region for this test is two-tailed, the critical values are:
±
I hope this helps!